Ruby Programming Language, Then Let's Proceed

Home , ERuby, Perl, Yukihiro Matsumoto

About the Tutorial Ruby is a scripting language designed by Yukihiro Matsumoto, also known as Matz. It runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.

This tutorial gives a complete understanding on Ruby.

Audience This tutorial has been prepared for beginners to help them understand the basic to advanced concepts related to Ruby Scripting languages.

Prerequisites Before you start practicing with various types of examples given in this tutorial, we are making an assumption that you are already aware of computer programs and programming languages in general.

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Table of Contents

About the Tutorial ......

Audience ...... i

Prerequisites ...... i

Table of Contents ...... ii

1. RUBY – OVERVIEW ...... 1

Features of Ruby ...... 1

Tools You Will Need ...... 2

What is Next? ...... 2

2. RUBY – ENVIRONMENT SETUP ...... 3

Try it Option Online ...... 3

Local Environment Setup ...... 3

Ruby Installation on Linux/Unix ...... 3

Using yum to Install Ruby ...... 4

Ruby Installation on Windows ...... 4

Ruby Command Line Options ...... 5

Ruby Environment Variables ...... 7

Popular Ruby Editors ...... 9

Interactive Ruby (IRb) ...... 9

What is Next? ...... 10

3. RUBY – SYNTAX ...... 11

Whitespace in Ruby Program ...... 11

Line Endings in Ruby Program ...... 11

Ruby Identifiers ...... 11

Reserved Words ...... 12

Here Document in Ruby ...... 12

Ruby BEGIN Statement ...... 13

Ruby END Statement ...... 14

Ruby Comments ...... 15

4. RUBY – CLASSES AND OBJECTS ...... 16

Defining a Class in Ruby ...... 17

Variables in a Ruby Class ...... 17

Creating Objects in Ruby Using new Method ...... 18

Custom Method to Create Ruby Objects ...... 18

Member Functions in Ruby Class ...... 19

Simple Case Study ...... 20

5. RUBY – VARIABLES, CONSTANTS AND LITERALS ...... 24

Ruby Global Variables ...... 24

Ruby Instance Variables ...... 25

Ruby Class Variables ...... 26

Ruby Local Variables ...... 27

Ruby Constants ...... 27

Ruby Pseudo-Variables ...... 28

Ruby Basic Literals ...... 28

Integer Numbers ...... 28

Floating Numbers...... 29

String Literals ...... 29

Backslash Notations ...... 30

Ruby Arrays ...... 31

Ruby Hashes ...... 31

iii

Ruby Ranges ...... 32

6. RUBY – OPERATORS ...... 33

Ruby Arithmetic Operators ...... 33

Ruby Comparison Operators ...... 33

Ruby Assignment Operators ...... 35

Ruby Parallel Assignment...... 35

Ruby Bitwise Operators ...... 36

Ruby Logical Operators ...... 37

Ruby Ternary Operator ...... 38

Ruby Range Operators ...... 38

Ruby defined? Operators ...... 38

Ruby Dot "." and Double Colon "::" Operators ...... 40

Ruby Operators Precedence ...... 41

7. RUBY – COMMENTS ...... 43

Ruby Multiline Comments ...... 43

8. RUBY – IF…ELSE, CASE, UNLESS ...... 45

Ruby if...else Statement ...... 45

Ruby if modifier ...... 46

Ruby unless Statement ...... 46

Ruby unless modifier ...... 47

Ruby case Statement ...... 47

9. RUBY – LOOPS ...... 50

Ruby while Statement ...... 50

Ruby while modifier ...... 51

Ruby until Statement ...... 51

Ruby until modifier ...... 52

Ruby for Statement ...... 53

Ruby break Statement ...... 54

Ruby next Statement ...... 55

Ruby redo Statement ...... 56

Ruby retry Statement ...... 56

10. RUBY – METHODS ...... 58

Return Values from Methods ...... 59

Ruby return Statement ...... 59

Variable Number of Parameters ...... 60

Class Methods ...... 61

Ruby alias Statement ...... 62

Ruby undef Statement ...... 62

11. RUBY – BLOCKS ...... 64

The yield Statement ...... 64

Blocks and Methods ...... 66

BEGIN and END Blocks ...... 66

12. RUBY – MODULES AND MIXINS ...... 68

Ruby require Statement ...... 69

Ruby include Statement ...... 70

Mixins in Ruby ...... 71

13. RUBY – STRINGS ...... 73

Expression Substitution ...... 73

General Delimited Strings ...... 73

Escape Characters ...... 74

Character Encoding ...... 75

String Built-in Methods ...... 75

String unpack Directives...... 85

14. RUBY – ARRAYS ...... 89

Creating Arrays ...... 89

Array Built-in Methods ...... 91

Array pack Directives ...... 99

15. RUBY – HASHES ...... 103

Creating Hashes ...... 103

Hash Built-in Methods ...... 104

16. RUBY – DATE AND TIME ...... 109

Getting Current Date and Time ...... 109

Getting Components of a Date & Time...... 109

Time.utc, Time.gm and Time.local Functions ...... 110

Timezones and Daylight Savings Time ...... 112

Formatting Times and Dates ...... 112

Time Formatting Directives ...... 113

Time Arithmetic ...... 114

17. RUBY – RANGES ...... 116

Ranges as Sequences ...... 116

Ranges as Conditions ...... 118

Ranges as Intervals ...... 118

18. RUBY – ITERATORS ...... 120

Ruby each Iterator ...... 120

Ruby collect Iterator ...... 121

19. RUBY – FILE I/O ...... 123

The puts Statement ...... 123

The gets Statement ...... 123

The putc Statement ...... 124

The print Statement ...... 124

Opening and Closing Files ...... 125

The File.new Method ...... 125

The File.open Method ...... 125

Reading and Writing Files ...... 126

The sysread Method ...... 126

The syswrite Method ...... 127

The each_byte Method ...... 127

The IO.readlines Method ...... 128

The IO.foreach Method ...... 128

Renaming and Deleting Files ...... 128

File Modes and Ownership ...... 129

File Inquiries ...... 130

Directories in Ruby ...... 132

Navigating Through Directories ...... 132

Creating a Directory ...... 132

Deleting a Directory ...... 133

Creating Files & Temporary Directories ...... 133

Built-in Functions ...... 133

File Class and Methods ...... 134

Directory Class and Methods ...... 139

20. RUBY – EXCEPTIONS ...... 142

vii

Using retry Statement ...... 143

Using raise Statement ...... 144

Using ensure Statement ...... 146

Using else Statement ...... 147

Catch and Throw ...... 148

Class Exception ...... 149

21. RUBY OBJECT ORIENTED ...... 151

Ruby Class Definition ...... 151

Define Ruby Objects ...... 151

The initialize Method ...... 151

The instance Variables ...... 152

The accessor & setter Methods ...... 152

The instance Methods ...... 155

The class Methods and Variables ...... 155

The to_s Method...... 156

Access Control ...... 157

Class Inheritance ...... 159

Methods Overriding ...... 160

Operator Overloading ...... 161

Freezing Objects...... 162

Class Constants ...... 164

Create Object Using Allocate...... 165

Class Information ...... 166

22. RUBY – REGULAR EXPRESSIONS ...... 167

Regular-Expression Modifiers ...... 167

Regular-Expression Patterns ...... 168

viii

Regular-Expression Examples ...... 171

Anchors ...... 173

Special Syntax with Parentheses ...... 174

Search and Replace ...... 174

23. RUBY – DBI ...... 177

Architecture of a DBI Application ...... 177

Prerequisites ...... 178

Obtaining and Installing Ruby/DBI ...... 178

Database Connection ...... 179

INSERT Operation ...... 180

Using do Statement ...... 180

Using prepare and execute ...... 181

READ Operation ...... 183

Fetching the Result ...... 184

Update Operation ...... 190

DELETE Operation ...... 191

Performing Transactions ...... 192

COMMIT Operation ...... 193

ROLLBACK Operation ...... 193

Disconnecting Database ...... 193

Handling Errors ...... 194

Code Blocks with Methods ...... 195

Driver-specific Functions and Attributes ...... 196

24. RUBY – WEB APPLICATIONS ...... 199

Writing CGI Scripts ...... 199

Using cgi.rb ...... 199

Form Processing ...... 200

Creating Forms and HTML ...... 201

Quoting Strings ...... 203

Useful Methods in CGI Class ...... 203

Ruby CGI ...... 204

Cookies and Sessions ...... 210

Ruby CGI Cookies ...... 210

Ruby CGI Sessions ...... 212

Web Hosting Servers ...... 214

25. RUBY – SENDING EMAIL ...... 215

Sending an HTML e-mail using Ruby ...... 216

Sending Attachments as an e-mail ...... 217

26. RUBY – SOCKET PROGRAMMING ...... 220

What are Sockets? ...... 220

A Simple Client ...... 221

A Simple Server ...... 221

Multi-Client TCP Servers ...... 222

A Tiny Web Browser ...... 223